Exercisers frequently build and tone their muscles by performing exercises on various exercise machines. A typical exercise is a chin-up during which the user grasps a pair of overhead handles or a bar and raises himself from a fully lowered position, in which the user's arms are fully extended, to a fully raised position, in which the user's arms are bent and the user's chin is substantially even with the pair of handles or bar. The user must lift his entire body in a conventional chin-up, and repeat the exercise for the desired number of repetitions. Unfortunately, for beginners, overweight individuals, or those with relatively weak upper bodies, a chin-up can be a very difficult exercise to perform even a single time, much less a number of repetitions.
Another fairly common and related exercise is the dip in which the user grasps a pair of handles with his arms straight and extended downward along his sides. The user then lowers his body weight while bending his arms. The user then raises his body weight by straightening his arms. At a conventional dip station, the user must support and raise his full body weight during the exercise; hence, a dip is also difficult for many individuals.
Exercise machines have been developed with conventional chin and dip stations, typically in combination with other weight training equipment. For example, U.S. Pat. No. 4,781,374 to Lederman discloses such an exercise machine. In addition, exercise machines have also been developed to assist a user in performing either a chin-up, a dip, or both. Accordingly, such machines permit a user to lift his body weight during a chin-up or dip while exerting a force with his arms less than his full body weight. This assistance permits beginners and others to perform a greater number of chin-up or dip repetitions to thereby gradually build their body strength.
There are several types of assisted chin and dip exercise machines. For example, U.S. Pat. No. 5,011,139 to Towley, III, entitled Assisted Dip/Chin Exercise Device discloses a weight-assisted chin and dip exercise machine including a foot bar upon which the user stands. The foot bar is fixedly secured to a pivoting arm which, in turn, is pivotally connected to the frame of the exercise machine. The foot bar is also coupled to a user-selectable amount of weight for urging the foot bar upwardly to assist the user in performing a chin-up or dip. Unfortunately, the foot bar provides an unstable support for the user to stand upon during operation as the foot bar rotates or rolls about its longitudinal axis underneath the user's feet while the user performs a chin-up or a dip. Moreover, the user may also be thrown from the machine if the user is not careful in stepping from the machine. Thus, the safety of the user may be compromised when using an exercise machine with a foot bar.
Another assisted chin and dip exercise machine is disclosed in U.S. Pat. No. 4,849,458 to Potts entitled Upper Body Exercise Apparatus. The patent discloses a pneumatically-assisted chin and dip exercise machine having a foot platform rather than a foot bar. The foot platform is connected to a frame by a mechanical linkage that slides and rotates relative to the frame such that the platform is restricted to vertical movement only as the platform moves up and down with the user. Although the user is assisted in performing chin-ups or dips, the restriction of the platform to vertical movement only does not permit the user's body to follow the natural arcuate path traced by the center of gravity of a user's body while doing a chin-up or a dip. Accordingly, the exercise is awkward and may produce undesirable stress on the arm and shoulder joints. Moreover, the targeted muscle groups may not receive the desired degree of training.
An exercise machine, whether for home or for fitness center use, is desirably relatively compact. Both chin and dip assist machines described in U.S. Pat. Nos. 5,011,139 and 4,849,458 require that the user be accommodated in the standing position. Accordingly, both machines are quite tall, making transportation and installation difficult. The exercise machine described in U.S. Pat. No. 4,849,458 also requires considerable clearance towards the front of the machine to permit free movement of the linkage connecting the foot platform to the frame.